Building (or other facility) sprinkler systems provide pressurized liquid (e.g., water) to extinguish or control a fire. A pump (e.g., a centrifugal pump) is used to provide the water pressure. The pump may be powered by an electric motor or other type of pump driver, such as diesel engine.
During actual operation in a fire fighting mode, water passing through the pump cools the pump and prevents it from overheating. Applicable code/regulations require that fire pumps must be periodically operated in a test mode to ensure reliability. During the test mode water is not delivered to the building sprinkler system. Instead, a small amount of water is delivered through the fire pump and diverted via a valve to an alternate path.
When the fire pump is driven, by an electric motor or by a diesel engine that is cooled by an engine mounted radiator (coolant to air) and fan, in pump test mode pressure builds up at the output side of the fire pump opening the alternate path that leads to drain. A small volume of water (e.g., 1-2% of fire pump rated flow) is delivered through the fire pump and then to the drain.
In the test mod, the small volume of water flow through the fire pump is sufficient for cooling the fire pump. However, the water is wasted by being delivered to the drain.